Electric switch



Feb. 16, 1943. M. c. HARROLD 2,311,048

ELECTRIC SWITCH Filed D90. 31, 1940 MGM INVENT R. M%

UNITED STATES i ELECTRIC SWITCH Marshall 0. Harrold, Dayton, Ohio,assignor to General Motors Corporation, Dayton, Ohio, a corporation ofDelaware Application December 31, 1940, Serial No. 372,527

-aTENT OFFICE 13 Claim.

This invention relates to refrigeratingapparatus and more particularlyto motor controls and electrical controls.

It is an object or my invention to provide an improved and simplifiedmotor control which will adequately control the starting and running ofthe electric motor and provide automatic protection against overloads.

It is another object of my invention to provide and fastened by therivet 28 to a pivoted annature 30. The rivet 28 also fastens a bimetalstrip 32 to the armature 30.. The pivoted armature 30 is provided withknife edges 34 which are adapted to rock upon the supports 22 with theleaf spring 24 in between. The leaf spring connects the armature 30 tothe supports 22 but allows the armature to rock upon the knife edges 34.A set-screw 36 extending through the base an improved and simplifiedsnap-acting mecha- 2D limits the movement of the armature 30 in a nismproviding excellent current-carrying propcounter-clockwise direction. I

erties which can be used either with a bimetal The leaf spring 24extends to an adjusting or another operating means. screw 38 extendingupwardly from the base. This It is still another object of my inventionto adjusting screw 38 is provided with a spring 40 provide anarrangement wherein a single bimetal and a nut 42 which is preventedfrom rotating strip may be caused to perform two control funcby a lipwhich is turned up at the end of the tions. leaf spring hinge. Byadjusting the screw 38, the

Further objects and advantages of the present nut 42 is raised orlowered in order to raise or invention will be apparent from thefollowing delower the end of the leai spring 24, which is heldscription, reference being had to the accombetween the nut 42 and thespring 40. This panying drawing wherein a preferred form of changes theangularity of the leaf spring 24 and the present invention is clearlyshown. thus changes the position of the armature 20 In the drawing: whenit is in open position and also changes the Fig. l is a top view of myimproved motor opening force of the armature 30, which opposes control;the attraction of its electromagnet 44.

Fig. 2 is a view in elevation 01' my improved The electromagnet 44 islocated between the motor control with the overload contacts in closedppo 21 d the lower 8nd of the armature position and theelectromagnetenergized and 30. The left end of the bimetal strip 32carries with the starting biinetal heated sufilciently to the startingcontact 48 which is adapted to make open the starting contacts; contactwith a stationary contact mounted upon is a view similar to Fig. 2 inwhich the an insulated post 48 which is fastened to the overloadcontacts are in open position and the base 20. The other end of thebimetal strip 32 electromagnet is consequently deenergized; carries theoverload contact 50, which is adapted Fig. 4 is a wiring diagram showingthe motor to make contact with a stationary contact mountcontrolembodiedin an electric motor circuit in ed upon an insulated post 52which is fastened one arrangement; to the base 20.

Fig. 5 shows the motor control embodied in an The contact 50 also servesas a rivet for i'aselcctric motor circuit in the arrangement showntening the bracket 54 to the end of the bimetal. inFigs.1 to 3; and Thisbracket 54 rigidly holds the two ends 0! a Fig. 6 shows the snap-actingmechanism emspring wire loop 56 which serves as a double bodied inanother form of control. toggle type snap-acting mechanism for the rightBriefly, I have shown an electric motor startend portion of the bimetalstrip 32. This loop ing and overload control including an electro- 56includes the arms 58 and 80 which have their magnet having a pivotedarmature carrying 9. ends extending into opposite sides of the bracketsingle bimetal strip in which one end serves to 54 to which they aresecurely fastened. These limit the energization of the starting windingportions 58 and 60 extend substantially parallel and the other endserves as an automatic overto the bimetal strip until they terminate atthe load control for the motor. A loop of spring wire sharp bends 62 and64. From the sharp bends is arranged so as to control the automaticover- 82 and 64 the portions 66 and 68 extend in the load portion of thebimetal strip with a double opposite direction, generally parallel, tothe portoggle type snap action. tions 58 and 60 as well as the bimetalstrip 32.

Referring to the drawing and more particu- These portions 86 and 68terminate in a looped larly to Fig. 1 there is shown a motor controlportion 10 which is hooked over the adjusting including a base 20, whichmay be formed of screw 12 with suflicient tension to properly metal orany other suitable material. Extending stretch the bimetal 32 and theloop 58 or spring upwardly from the base are a pair of supports wire.The tension should be such as to cause designated by the referencecharacter 22. Fasthe end of the bimetal strip to snap to open and tenedto the sup orts .22 is a l af spring hinge closed positions when heatedand cooled as illusconstruction including the leaf spring 24 whichtrated in Figs. 2 and 3. The spring wire loop is i'astened by the rivets26 to the supports 22 (i0 56 constitutes a double toggle typesnap-acting mechanism without any frictional connections so that it willbe more accurate than toggle mechanisms of other types.

In Fig. 5, there is shown diagrammatically an electric motor 14 having amain winding it and a phase winding it. The junction of these twowindings is connected to a supply conductor 80 under the control of asuitable control switch 82. The other end oi. the main winding 1% isconnected by the conductor 86 to the electromagnet 44 which in turn isconnected to the support 22. The phase winding 18 is connected by theconductor 86 to the contact post d8 which in turn connects to themovable contact 46 provided upon the end of the bimetal 32. This end ofthe blmetal 32 carries the phase winding cur-= rent while the other endcarrying the contact 50 carries both the main and the phase windingcurrent. The contact 58 connects to the contact post 52 which in turnmay be connected to a heater 54 for applying additional heat to thebimetal 32, if this is found necessary. This heater :3 is connected bythe conductor 88 to the supply conductor 96.

In this system, when the switch 82 is closed, current will flow from theconductor 8d through the main winding it, the conductor 84,electromagnet 44 and the right end of the bimetal strip through contacts50 and 52 and the conductor 88 to the conductor 90. This will causeelectromagnet 44 to attract its armature 30 and to cause the contact 46to engage the contact on top of the insulating post 48. This will causecurrent to flow through the phase winding E8, the

conductor 86 and the contact 48 as well as the entire length of thebimetal strip 32. This energization will cause the motor 54 to start andpick up speed.

The system is provided with two means for deenergizing the phasewinding. It is well known that, as an electric motor picks up speed, thecurrent consumption falls off. This reduces the flow of current throughthe electromagnet i4 and the opening force provided by the leaf spring24 will cause the contact 45 to be raised when thecurrent falls offsufliciently. The other opening means is the bimetal 32 itself whichwill be heated by the flow of the phase winding current through it sothat it will curl upwardly and lift the contact it away from the post 33to deenergize the phase winding. Thus, whichever of these means isfirst, will control the opening of the phase winding contacts. Undernormal voltage conditions the electromagnet 36 will open the contactsprior to the opening by the bimetal 32, but under high voltageconditions the elec= tromagnet 45 does not open the contacts soon enoughso that the bimetal 32 takes care of this under those circumstances.

In Fig. 4, the circuit is substantially the same and all parts of thecircuit with one exception are given the same reference characters. Thedifference between the circuit of Fig. 5 and cir cult of Fig. 4 is that,instead of the electromag= net 45 being connected to the support 22,-the electromagnet 44 is connected by a pig-tail connection 94 with thecontact 46. With this construction the entire motor current passesthrough the bimetal 32 from one end to the other. upon the left portionof the bimetal 32 so that this bimetal may be made wider than in theother construction. In all other respects the circults are the same andthe circuit and the control operates in the same manner.

This provides a greater heating effect In Fig. 6 I have shown mysnap-action mechanism incorporated in an ordinary switch. In thisswitch, there is provided a supporting means ml which is connected tothe source conductor 503. The current-carrying flexible strip of springmetal N35 has one end anchored to the supporting means iti and extendsin cantilever fashion therefrom to a bracket iil'i which is ias tened tothe end of the strip m5 by the movable contact 509. This movable contactW9 is adapted to make contact with the stationary contact provided uponthe top of the insulating post Hi. This stationary contact is connectedto the other source conductor l is. My wire loop snap-acting mechanismH5 is connected to the bracket it? as shown in Figs. 1, 2 and 3, and thespring wire is made in the same form shown in these figures. However, inFig. 6, instead of the wire loop its hooked over the adjusting screw 12it is looped over the end oi an adjustment lever H9 provided upon theend of a lever arm i ii. The adjustable lever H9 holds the flexiblestrip Hi5 and the spring wire loop snap-acting mechanism Hi5 a stretchedcondition. A set-screw i2! is p ovided for adjusting the tension appliedto the spring wire loop Hi5. A bellows or any other suitable means maybe used to operate the lever Hill to cause the contact N39 to be snappedto open and closed positions just as is shown in Figs. 2 and 3. Thus itwill be seen that this simple snap action mechanism may be applied todiilferent types of contact problems.

While the form of embodiment of the invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. In combination, a supporting means, :2. flexible strip anchored atone point to said supporting means and extending in cantilever fashiontherefrom to provide a movable extension, spring means having a firstportion rigidly connected to said extension and extending therefrom in adlrection substantially parallel to the strip to a first point adjacentthe anchorage of the strip and a second portion extending from saidfirst point to a second point adjacent the rigid connection, and meansconnected to the spring means for holding the flexible strip in tension.

2. In combination, a supporting means, a flexible strip anchored at onepoint to said supporting means and extending in cantilever fashiontherefrom to provide a movable extension, spring means having a firstportion rigidly connected to said extension and extending therefrom in adirection substantially parallel to the strip to a first point adjacentthe anchorage of the strip and a second portion extending from saidfirst point to a second point adjacent the rigid connection, and meansconnected to the spring means for holding the flexible strip and thespring means in a stretched condition.

3. In combination, a supporting means, a hexible strip anchored at onepoint to said supporting means and extending in cantilever fashiontherefrom to provide a movable extension, spring means having a firstportion rigidly connected to said extension and extending therefrom in adirection substantially parallel to the strip to a first point adjacentthe anchorage of the strip and a second portion extending from saidfirst point to a second point adjacent the rigid connection, saidflexible strip being provided with means for causing itself to snap toopposite sides of said spring means under the control of said springmeans.

i. In combination, a supporting means, a bimetal strip connected to andextending from the supporting means, a double-back type means having afirst portion rigidly connected to a point upon said strip and extendingfrom said point generally parallel to the strip to a second pointadjacent the connection of the strip with the supporting means andhaving a second portion extending from said second point to a thirdpoint adjacent the rigid connection, a spring means connecting to saidsecond portion adjacent said third point and means connecting to saidspring means adjacent said third point, said strip and said first andsecond portion being displaced to allow the strip to move to oppositesides of the dead-center position.

5. An electrical control including an electromagnet and a movablearmature for said electromagnet, a bimetai strip supported upon saidarmature having its ends extending in opposite directions therefrom,contact mechanisms connected to said strip on opposite sides of saidarmature, and a snap-acting mechanism for controlling the operation ofone of the contact mech anisms independently of the other, said othercontact mechanism being operated by the movement of the strip.

6. An electrical control comprising a supporting means, a binietal stripsupported at an intermediate point upon said supporting means and havingportions extending in opposite directions therefrom, a contact mechanismconnected to and operated by each of said portions, and a snapactingmechanism for controlling the operation of one of the contact mechanismsindependently of the other.

7. In combination, a supporting means, a fiexible strip anchored at onepoint to said supporting means and extending in cantilever fashionthereirom to provide a movable extension, spring means having a firstportion rigidly connected to said extension and extending therefrom in adirection substantially parallel to the strip to a first point adjacentthe anchorage oi the strip and a second portion extending from saidfirst point to a second point adjacent the rigid connection, meansconnected to the spring means ior holding the flexibis strip in tension,and switch contact means connected to and operated by said movableextenslon.

8. In combination, a supporting means, a flexiblo strip anchored at onepoint to said supporting means and extending in cantilever fashiontherefrom to provide a movable extension, spring means in the form ofspring wire having two portions rigidly connected to said movableextension and extending therefrom in a direction substantially paralleito the strip to points upon opposite sides of the strip adjacent theanchorage of the strip, said spring wire extending substantially in theopposite direction from said points to a third point adjacent the rigidconnection, and means connected to the spring means :ior holding theflexible strip in tension.

9. a a flexiblc strip anchored at one point to said supporting means andextending in cantilever fashion therefrom to provide a movableextension, spring means in the form oi two portions rigidly connected tosaid movable extension and extending therefrom in a directionsubstantially parallel to the strip to points upon opposite sides of thestrip adjacent the anchorage of the strip, said spring wire extendingsubstantially in the opposite direction from said points to a thirdpoint adjacent the rigid connection, means connected to the spring meansfor holding the flexible strip in tension, and a control device operatedby the movement of said movable extension.

10. In combination, a supporting means, a flexible strip anchored at onepoint to said supporting means and extending in cantilever fashiontherefrom to provide a movable extension, spring means in the form ofspring wire having two portions rigidly connected to said movableextension and extending therefrom in a direction substantially parallelto the strip to points upon opposite sides of the strip adjacent theanchorage of the strip, said spring wire extending substantially in theopposite direction from said points to a third point adjacent the rigidconnection, means connected to the spring mean:, for holding theflexible strip in tension, and means for providing relative movementbetween the portion of the spring wire adjacent said third point and therigid connection.

11. In combination, a supporting means, a flexible strip anchored at onepoint to said supporting means and extending in cantilever fashiontherefrom to provide a movable extension, a unitary member having afirst portion rigidly connected to said extension and extendingtherefrom in a direction substantially parallel to the strip to a firstpoint adjacent the anchorage of the strip and a second portion extendingfrom said first point to a second point adjacent the rigid connection,said strip and said first and second portions being displaced to allowthe strip to move to opposite sides of the dead-center position, aportion of said unitary member being resilient, and means connected tosaid unitary member adjacent said second point for holding said nexiblestrip in a stretched condition.

12. In combination, a supporting means, a movable member connected atone point to the support and extending in one direction therefrom, aspring wire member having a. first portion connected to said movablemember at another point and extending directly from said another pointsubstantially in a straight line to a first pointadjacent said one pointand a second portion extending substantially in a straight line directlyfrom said first point to a second point adjacent said another point, andmeans connected to the spring wire member adjacent said second point forplacing the spring wire member and the movable member in tension.

13. in combination, as. supporting means, a flexible strip anchored atone point to said supporting means and extending in cantilever fashionthere from to provide a movable extension, 9. spring wire member havinga first portion rigidly connected to said extension and extendingtherefrom in a direction generally parallel to the strip to a firstpoint adjacent the anchorage of the strip and a second portion extendingfrom said first point to a second point adjacent the rigid connection,and means connected to the spring member for holding the flexible stripin tension.

MARSHALL C. HARROLD.

